During the initial theatrical run of the Neon Genesis Evangelion films, theatrical program books were sold in the theaters screening the films. This is common practice in Japan. The Evangelion program books contain glossaries, timelines, interviews, production notes, plot notes, and more. These books are especially interesting because they were specifically approved by Studio Gainax and the producers of Evangelion. Thus they offer a rare look at Evangelion from the creators themselves. They are canon and official.